The objective of this study is to establish the effects of effective antiretroviral therapy on T cell dynamics, nutrient metabolism and apoptotic pathways in AIDS patients. A combined protease inhibitor regimen (ritonavir/sequinavir) will be given to previously PI-naive or indinavir-failure patients (viral load >10,000). A new method for directly measuring CD4 + CD8+ T-lymphocyte proliferation and destruction (turnover) will be performed, before and at therapy (N=18). Sophisticated trace element kinetics and nutrient metabolism will be performed on another subset (N=18). Apoptotic pathways, body composition and other end-points are also measured. The interaction with nutrient supplementation will also be tested.